Process of heat treating ferrous metals



Patented Jan. 9, 1934 UNITED STATES PROCESS OF HEAT TREATING FERROUSMETALS V James A. Robertson and David Robertson, To-

ronto, Ontario, Canada, assignors of one-half to George F. McCandless,Toronto, Canada No Drawing. Application June 20, 1932 Serial No. 618,297

Claims.

The principal objects of this invention are to enable the conversion oflow carbon ferrous metals such as iron or soft steels into high carbonsteel with an increased tensile strength and hard- 5 ness in aremarkably short period and at very moderate cost.

The principal feature of the invention consists in the novel admixtureof materials in which the metal to be treated is packed to be heattreated whereby the grain of the metal is affected to increase porosityand a high percentage of silicon content of the metal is removed and aremarkable degree of'penetration of other metals and carbon are effectedin the minimum of time.

According to this process a thorough mechanical mixture of materials infinely ground or powdered form is prepared in or about the followingproportions Percent Charcoal 40 Hardwood Sawdust 24 Chromium 5 Manganese20 Borax 8 25 Pea chop 3 The metal to be treated is packed in suitableiron boxes or flasks, each piece being completely surrounded with theground mixture as is the usual practice for pack treatment.

The flasks are then placed in a suitable furnace and are brought to atemperature of from 1850 F. to 1950 F. and retained under suchtemperature for a period sufficient to obtain the desired penetration,it being found that treatment at the above temperature obtainsapproximately 1%" of penetration in two hours and the admixture ofmaterials is such that any degree of penetration up to completepenetration may be obtained.

It will of course be understod that the dimensions and volume of themetal pieces being treated will require widely varying periods of timeto attain the furnace temperature and that the treatment is carried onin periods of time to attain the furnace temperature and that thetreatment is carried on in periods, following complete heat penetration,in accordance with the desired carbon penetration.

The use of borax with the manganese and chromium salts is found toproduce an extremely desirable result in effecting deep penetration ofthe foreign metal substances into the iron or mild steel being treatedand the penetration is assisted by the continued supply of carboneffected by the presence of the pea chop and hardwood saw dust followingthe initial application of carbon supplied by the charcoal.

The pea chop, which consists of pea vines, pods and peas finely chopped,with the hardwood sawdust, provides a solid base for the metal to 50 betreated and prevents warping.

Under the heat-treatment the pea chop has the effect of opening thegrain of the metal thereby assisting the penetration of the borax whichacting as a purifier removes corrosion in the metal 5 and eliminates aportion of the silicon.

The opening of the grain permits the ready penetration of the manganeseand chromium and also the carbon produced by the charcoal and sawdust.The use of sawdust maintains the production of carbon beyond the periodof the production of carbon from the charcoal in the mixture.

Ferrous metals heat treated in the manner described have a hard but notbrittle surface and a very desirable quality of steel is produced.

It will of course be understod that the proportions of the materialsused may be varied in accordance with the quality of the metal beingtreated.

What we claim as our invention is:-

1. A process of heat treating ferrous metals, consisting in firstpreparing a mixture of finely ground carbonizable materials, manganese,chromium and borax, then packing the metal articles to be treated insuch mixture, then raising the temperature of the entire body ofmaterials to from 1850 F. to 1950 F. and maintaining such temperaturefor a period to effect the desired penetration of the resultantsubstances into the grain of the metal.

2. A process of heat treating ferrous metals, consisting in preparing amixture of finely ground materials in or about the followingproportions:

Per cent Charcoal 40 Hardwood sawdust 24 Manganese 20 Chromium 5 Borax 8Pea chop 3 then packing the metal articles in such mixture, then heatingthe mass to attain a temperature of from 1850 F. to 1950" F. andmaintaining such temperatures for a period of approximately two hoursfor each of carbon penetration of the metal desired.

3. A process ofheat treating ferrous metals, consisting in firstpreparing a mixture of finely the desired penetration of the carbon,manganese and chromium into the grain of the metal.

4. A compound for use in the heat treating of ferrous metals containingmanganese, chromium, borax and a carbonizable material.

5. A compound for use in the heat-treating of ferrous metals containingmanganese approximately 20%, chromium approximately 5%, boraxapproximately 8%, in combination with approximately 67% carbonizablematerial.

JAMES A. ROBERTSON. DAVID ROBERTSON.

